Melt butter over low heat and whisk in flour. Whisk frequently, and continue cooking over low heat until the roux is golden brown.
Whisk in chicken broth until it is combined with the roux. Increase heat to medium, and stir frequently. Add old bay seasoning, onion powder, tomato paste, sherry, cream. Simmer gently for 10-15 minutes.
Add seafood and heat gently for 3-4 minutes, or until heated through. Serve immediately.
Notes
You can use raw seafood if you would like in this recipe, just make sure to simmer it in the soup for 2-3 minutes to cook it through. I just happened to have the seafood already cooked on hand, so didn't do that this time.